The Apache projects are defined by collaborative consensus based processes, an open, pragmatic software license and a desire to create high quality software that leads the way in its field.

The ASF is made up of more than 150 top level projects which cover a wide range of technologies. Chances are if you are looking for a rewarding experience in Open Source, you are going to find it here.

Apache Tomcat is a web server that is an open source software
implementation of the Java Servlet and JavaServer Pages technologies.
The Java Servlet and JavaServer Pages specifications are developed under
the Java Community Process. Apache Tomcat is developed in an open and
participatory environment and released under the Apache License version 2.
Apache Tomcat is intended to be a collaboration of the best-of-breed
developers from around the world. We invite you to participate in this open
development project.
Apache Tomcat powers numerous large-scale, mission-critical web applications
across a diverse range of industries and organizations. Some of these users
and...

Apache Thrift allows you to define data types and service interfaces in a simple definition file. Taking that file as input, the compiler generates code to be used to easily build RPC clients and servers that communicate seamlessly across programming languages. Instead of writing a load of boilerplate code to serialize and transport your objects and invoke remote methods, you can get right down to business.